Centrifugal separation



Feb. 16 1926.

J. M. NlcOL CENTRIFUGAL SEPARATION Filedmsept. 2e, 1923 3111.09 tot WMM??? Cui lll

' the mostcllicient centrifugal action it is Patented Feb. 16, 1926.

PATENT OFFICE.

JOHN M. NICOL, OFT/LILI; VALLEY, CALIFORNIA.

CENTRIFUGAL SEARATION.

`Applcation filed September 26, 1928.

To all cto/loin it muy concern.' lie it known that l, JOHN MALCOLM NicoL, a subject of the ling ot Great Britain, a resident ot Mill l/Tallev, in the county of Marin and State oi California, have invented a certainnew and usei'ul Centrifugal jieparatiou, ol which the following is a specilication.

This invention relates to a profess of centrifugal separation and more particularly to a process of centrifugally separating 'mined materials, ores, minerals, or line ore slimes.

The invention has as an object the separation o1" ores or minerals from each other such as are. diiiicult or expensive to separate by vflotation processes or other` means. It has also as ,an object the separation ot mixed slime sulphide concentrates from oil lietation processes where selective flotation has tailed ot application or where the slimes are too line to treat by wet table concentration. A. further object is to make a substantially quantitative separation of such ores or minerals and to accomplish this rap- 'dly andrelatively inexpensively. Furthermore, a special object of the invention is to separate noble metals like gold and platinum Jfrom associated minerals by a centrifugal process. Further objects ot the invention will beco ne apparent as the description proceeds. Y

. ln accon'iplishing these objects and carryingout the invention l employ centrifugal torce to act upon the materials and to arrange them in concentric layers ot prog: sively 'varying densities. ln order to oh un desirable to treat the materials in a linely comminuted or divided state, preferably in the form ot tine aqueous pulp or in the torm ot slimes. Although the separation of the different minerals into concentric layers by Vcentrifugal force is both effective and rapid,

the ditiiculty in the practical application of this method to the art has consisted in obtaining a substantially complete separation 'ot the different layers from each other, and especially in obtaining` a continuous discharge of the individual concentrates a separate products. As far as the ditiiculty,

has resided in a proper form ot apparatus,

l believe l'liave solved this phase oit the matter by the invention disclosed in my application, Serial No. 659,727 of August 28, 1923,

Serial No. 665,007'.

wherein l have discloseda centrifugal machine of wel-balanccd construction havingl an inner fixed or rotatable bowl for causing` a ditl'crential movement ot' the materials, and having an upper adjustable bowl Yfor pro- `riding two cutouts ifor the mineral layers. Apparatus is designee also to operate with a column or wall oit' mercury subjected to rapid rotation for the purpose not only of allowing the aqueous mixture or pulp to pass freely upwardly, but also of collectingr heavy metals like gold.

liy way of a more detailed description of the apparatus referente is made to the accompanying drawing, in which,

`Fig. 1 represents a vertical central scction ot the centrifugal Separator; and

Fig. 2 represents a modilication of a part ot he structure comprising the inner bowl.

ln the drawings there is shown a main supporting trame 1 that carries an upper cr member 2 and a lower cross member 8. 'lhe upper cross member carries a removable angle bracket 4 serving as the supporting means for an upper bearing', and the lower cross member carries another removable angie bracket 5 serving to support a lower bearing, these bearings serving to support the revolving parts to be described later. There is also provided a footstep bloei: 6 having an oil well 7 and anadjustable center pivot 8, and a preferably brass hushed central vertical bearing 9.

The main revolving member in which the centrifugal etlect is produced cons ts ot' a bowl 1() into the bottom oi which is screwed a Ytootstep sha't 11 held b v a set screw 12. The shalt 11 revolves freely in the bearing 9 and rests on the pivot oi the screw 8, this mechanism being finely balanced so that the bowl will not revolve irregularly during operation. 'lhe said bowl is provided with two interior annular rillies 13 and la and a large annular concave riil'le 15 designed to contain mercury in this particular e111- bodinient. There is also a discharge orilice it provided with a removable plug.

A central vertical feed pipe 17 is screwed into the bottom ot the bowl 10 at a socket 18, and is provided with three openings near the said socket, one of which, 19, is shown. Said pipe 17 also serves as the driving member for the bowl 10, and for this purpose lo-cated a simple clamp collar 26, heldwith set screws, and a flat disc 2T is located thereon and connected to the massive ring @e by a short cylindrical section ot pipe 28. The three n'iembers 2d, 27 and 28, are joined together Aand supported by the pipe'i, as will be evident, thus forming a single nonrotating member, which may be termed an inner guide bowl. As ,will be seen, this is stationary in the embodiment now heilig de* scribed.

ibove the disc 27 is provided a'rball bearing 29 on which runs an upper rotating hood bowl 30, which is suitably connected to and driven by a horizontal pulley 3l provided with a bearing' Said hood bowl BOhas an inner annular concave groove that is provided with a number of discharge openings such as 34C.

lt will be seen that the space between the lower bowl lO and the .upper hood bowl 30 represented by numeral 35 constitutes an annular discharge orifice 'for theY concentrates oit vhigher density congregating against the inside of the bowl l0, and this y space 35 may be decreased or increased by manipulation of the screw 8 so that an opening as line. as l/lOO may be obtained. A noteworthy feature oic this structure is that suehla tine adjustment may be made 'during the operation of the apparatus, thereby making it possible to obtain a clean separation during` the running ot the machine byobservat-ion of the nature and qr-.alityof the concentrate issuing' through said opening 35. rlhe discharge ot concentrates coming' through the annular opening will fall into a suitably placed launder shown at 36. The concentrates lying inside of the outer ring of heavier concentrates may be made to pass out through the openingsje and will be discharged into an outer laundei' shown `at 37.

A wooden plug 38 may be inserted in the bottoni oit the pipe l? to close the same be-Y low the orifices 19.

ln Fig. 2 a modiication is illustrated, showing a construction in which the inner bowl may be made rotatable. A cross ineinbei' 2 carrying a bracket l supports a bearing 2l around a centrally litted pipe 17. A central pipe 22 is mounted over the said bearing 2l and .has screwed at the upper end thereotl a driving member 39 rotat- -oit the inner concentric columns.

navarros ing upon ball bearing 40. A bearing ll inserted in the bracket 4 serves to guide pipe 22. The latter is therefore made ro Ytatable and consequently the corresponding ture being the. saine as in the above-described preferred embodiment. l

ln centrifugal methods the principal ditiiculty has been to separate the diliferent lay- Y ers owing tothe thinness of some o1 them, since it isfahnost mechanically impossible .l'ect a entrait ot such a thin layer, and

'furthermore impossible to eliect a ine- .nical cutout of thick layers since there will be iutei'n'iingling ot materials. k lfor eX- ample, in the case vot silver-lead, pyritic and sine ore, the particles ot the silver-lead shines would have a .specilic gravity of' about and would form the outer layer and probably would not exceed l/lOG oit an inch in thickness. rilhe next layer would be the pyritic material having a specific gravity ot 4.5, which layer vwould be generally thicker. To separate these two layers by mechanical means is obviously hopeless.

ln order to effect a substantially coinpl te separation. ot suoli layers resulting Vfrom a centrifugal process, l have invented lis te increase the balk ot material between the layers so that a lwide zone will exist be tween the minerals and a clean cutontcan easily be made.

'lhe invention may oliviouslyv be carried out in a n'iultitude of ways widely dissimilar to minerals and separating' media and, therefore, it will sunice to give a. few exanr ples with respect to particular oes and minerals. ller example, in the case of the silver-lead, pyritic, zinc ore mentioned, barytes may be added to the mixture to form a dividing medium between the silver-lead and the pyritic minerals, inasmuch as' it has a density o'l' about 5.*l`he order of the concentric columns ol' ascending pulp would. then be: l. silver lead, 2. barytes, 3.' pyritic materials, and el. the remainder l By using the apparatus above reterredto two groups ot products would be obtained, namely, first, the silver-lead concentrate with part of the barytes, andsecond, the remainder of the barytes, together with the rest of the inaterial in the form ot' a mixed product. By taking the irst product and passingl it through a simple flotation cell the barytes would be thrown down and could be used over again in'a closed metallurgical circuit andthe silver-lead product would then be delivered as a clean concentrate. l

The d' riding' media should preferably be neutral with regard to subsequent metallurgical treatments. For example, the ba rytes suggested above as a mediun'i is not alected by `flota-tion, whereas silver-lead conc x1utrates are4 readily an'ienable to flotation. I gnetite is another suitable medium inasmuch as it can be used between non-magnetic sulphides and can subsequently be separated out by magnets and then returned 'for re-use. lt the medium used can be ol'itained in abundance and cheaply it mightbe possible in many cases to omit the separation of the medium and concentrate and to smeltthei'n together directly. In order to obtain a suitable density it may be desirable to manufacture a` suit-able medium by grinding to a'ether suitable minerals having' the proper densities or by providing any other suitable material having the required density. The question of the selection of media depends entirely upon the nature of the minerals or ores beingtreated'a-nd the character ot subsequent operations.

As a still further example of a mineral treatment may be given an ore carrying the following materials: gold, free and in fracture planes of pyrites and arsenical pyrites; complex silver sulphides and arsenides together with tellurides of silver and gold; galena, associa-ted with gold and silver sulphides; antimonial silver, occurring as steplienite or tetrahedrite; zinc, sulphide or sphalerite; molybdenite; pyritic minerals. in this particular art the minerals of eco nomic importance are gold, molybdenum, silver-lead, and possibly Zinc. By the use ot the centrifugal machine gold would be driven into the mercury layer with orwithout. amalgffimation, amalgamation not being essential in this process; the silver sulphides and ameno-minerals with the exception of tetrahedrite, would pass with the galeria and may be separated out by a dividing medium consisting of ilmenite having a density ot 5. The lirst treatment would, theretore.y result in: l. gold; 2. silver-lead concentrate carrying some arsenical pyrites, together with a portion of the ihnenite; 3. the remaining' ilmenite, plus a mixed pyritic concentrate and tailings carrying' also the sphalerite and molybdenite. Product No. 2 could be directly treated or sold as it is of value, while product No. 3 would be passed through a second centrifugal machine, using` this time as a dividing medium either celestite or a selected garnetl sand or a hematite Sand or an artificial product having' a density ol" l to 'lhere would then result l'rom this third product two sub-products as iollows: (a) a pyritic concentrate carrying tetrahedrite and the inolybdenite, (o) sphalerite and any iniddlings or tailings sands. This is as far as it would be adv'jable to no with the centrifugal separation, since the pyritic group and the molybdenite are too near in their rcspt-ctive densities.

It will be apparent in Y above example that an orc or mineral niiiture may be :ulvantagretnisly and succesf'slul v treated by the above described centrifugal whereas it would be econtnnicaly ile to do much with such an orc by means of any other known process. Many other adaptations o'l the invention will sua# gcst themselves to those skilled in the art upon considering' the use oi: the above process, particularly in connection with my centrifugal machine above mentioned.

.tis many apparently widely different enibodiments of my invention may be made without departing; from the spirit thereof. it to be understood that I do not intend to limit myself to the embodiments described except as defined in the Afollowing claims.

. l. The process oit substantially completely separating` mineral particles having' diilierent densities, comprising adding' thereto a material having` an intermediate density and centrilugalizing the mix to obtain concentric layers with the added material positioned between the minerals to be separated, and el'iecting` a cutout of a mineral-layer at some point within said intermediate layer between the planes ot the outer layers.

2. The process ot claim l wherein the centriitugalizing` is performed within a substantially vertical rotating' column of mercury at the top of which is provided a cutout for the outer mineral layer.

3. The process of claim l wherein the minerals are .Q'iven a dill'ercntial movement dur-- ing;l centritugalizing'.

fl. The process oi claim l wherein the1nincrals are in the iorm of a line ore pulp containingconsiderable quantities ot mi2-:cd sul phide concentrates.

5. The process of claim l wherein the minerals are in the orin ot a tine ore pulp containingl sulphides of silver-lead and zinc, and pyrites, and the first cutout is a silverlead concentrate.

(i. rEhe process of separatinp` mineral particles consisting' in adding' to a mixture oit such particles a material ot specific gravity intermediate the specilic `gravity ot such particles and nonresponsive to selective liotation7 stratityinp,` the mixture according;` to specific gravity, cutting out a layer from the stratified mass and subjecting the mateconsideringl the Hill Vrial so cut out to selective flotation to separate the desired mineral from noii-iiotative and added matter.

7. rlhe process of separating mineral particles having dii'erent densities, comprising subjecting them to centrifugal action in the 'forni of an aqueous finely sub-divided mixture in Contact with an outer rapidly rotating wall oiQ mercury along which the materials pass, Vand are formed into layers, and thereupon effecting a cutout in said layers at the top of the wall of mercury between the planes of the outer layers.

8. The process of substantially completely separating)l mineral particles having different densities comprising adding thereto a non-mercurial materia-l having` an'intermediate density and centrifugalizing the mix in Contact with a rotating` wall o niercury to obtain concentric layers with the added material positioned between the min- ,erals to be separated, and eti'ecting a cutout oi' a mineral layerl at some point within said intermediatel layer. Y

9. The invention in claim 8 wherein the cutout is above the top of the wall of mereA cury.

a non-mercurial material having an inter-V mediate density and progressively introduc- 10. The process of substantially completeingI and centrifugalizing the mix in rela tively 'thin layers in contact with a rotating,` wall of mercury to obtain concentric layers with the added material positioned between the minerals to be separated, and effecting a cutout Vof ainineral layerL at some point within said intermediate layer. ll. The process of separating mineral particles having' diilerent densities, comprising adding` thereto a material having an intermediate density and eentritugal'izing the iniX to obtain relatively thin concentric layers with the added material positioned between the minerals to be separated, and eil'ecting a cutout of a mineral layer at the top of the layer and at some point within said intern'iediate layer between the planes or' the outer layers. p

l2. The process of separating` mineral particles having different densities, coinprising subjectingl them in the forni of' a iinely divided mixture containing added non-mercurial material, to centrifugal action in contact with a rotating wall of mercury, causingthe minerals to iforin into thin cmicenti'c layers inside oit the mercury wall, and effecting al cutout in a layer between ythe planes of the outer layers.

in testimony that li claim the foregoing, l have hereunto set my hand this 24th day 'i' September, 1928. i

JOHN NICOL. 

